Mechanism of catalytic hydrogenation of but-1-yne on palladium
- Universite Louis Pasteur, Strasbourg (France)
The deuteration mechanism of but-1-yne on differently dispersed Pd/Al{sub 2}O{sub 3} catalysts (D = 26%, >80%) was studied at 293 K. Experiments were performed by flowing a hydrocarbon square pulse at constant pressure (15 Torr) and a H{sub 2}-He carrier gas (37-708 Torr) onto the catalyst. Three stages were observed, namely (i) an initial stage with high activity and very low selectivity; the duration of this stage was proportional to the palladium weight and the number of hydrocarbon molecules which passed through the catalyst; (ii) a steady-state stage with constant activity and 98% but-1-ene selectivity; using microwave spectroscopy the authors found that in addition to the cis addition of two deuterium atoms, 10 to 20% of but-1-ene were produced by a different route; (iii) a final stage in which, when the hydrocarbon pressure decreased in the gas phase, an additional desorption peak was obtained consisting of C{sub 4} hydrocarbons. It is proposed that the palladium surface during the steady state is covered by strongly but reversibly adsorbed but-1-yne molecules which act as a poison and are in equilibrium with the reactive chemisorbed but-1-yne molecules. The reactive molecules are described as vinylic adsorbed species in equilibrium with carbene and carbyne species. The first lead to a cis addition mechanism. The latter two lead to the trans addition and direct hydrogenation.
- OSTI ID:
- 7128622
- Journal Information:
- Journal of Catalysis; (USA), Vol. 114:2; ISSN 0021-9517
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALKYNES
HYDROGENATION
PALLADIUM
CATALYTIC EFFECTS
ALUMINIUM OXIDES
BUTENES
CATALYST SUPPORTS
CHEMICAL REACTION KINETICS
DEUTERIUM
LAYERS
MICROWAVE SPECTRA
POISONING
SURFACE PROPERTIES
ALKENES
ALUMINIUM COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
ELEMENTS
HYDROCARBONS
HYDROGEN ISOTOPES
ISOTOPES
KINETICS
LIGHT NUCLEI
METALS
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
REACTION KINETICS
SPECTRA
STABLE ISOTOPES
TRANSITION ELEMENTS
020400* - Petroleum- Processing